The invention relates to a device for determining a load on a hoist, in particular a hoist of a crane for handling a container, including at least one rope drum, at least one drive motor as well as a hoist transmission disposed between drive motor and rope drum and arranged in a hoist transmission case which is supported on one side of the hoist frame, wherein the hoist transmission case is swingably supported in the area of one of its end faces about an axis in parallel relationship to the rope drum axis and supportable in the area of its other end face on at least one torque support, to which a measuring unit for indirect determination of the load, suspended from the ropes, is associated.
The determination of the load received by the crane is of primary concern if cranes are involved that operate automatically, in particular cranes for handling containers. It contributes to the safety of the crane and thus of the personnel entrusted therewith, so that the crane can be shut down in case of, e.g. overload, serves as scale for ascertaining the load and its load distribution in the ropes, or determines the center of gravity of the load itself, e.g. when the containers are loaded unevenly. Finally, the load determination serves also as indicator for static determination of maintenance periods in connection with the elapsed running time.
Conventional assemblies provide load determination in the rope or in the hoisting device. It is known to measure the axial force in the hoist transmission, caused by the oblique toothing of the spur gears, as proportional variable of the rope force; however, the load measurement is inaccurate and thus has failed. Interfering influences as a result of heat expansion and external temperature impacts can only be compensated in a very complicated technical manner.
According to a conventional technique to determine the load employs the support of the hoist transmission on a torque support. The support force measured hereby on the torque support is proportional to the rope force and thus to the mass suspended from the ropes. The load determination works fairly simple so long as all of the ropes, unspooled from the rope drums, are guided tangentially in the same direction. However, in the event the ropes are paid out in different directions, the conventional load determination is not possible via the torque support.
When several lifting ropes are wound on a common drum, the rope force can be measured in each rope strand. A measuring device is hereby installed on the rope end. Then, the sum of all measured rope forces corresponds to the mass of the load. The measuring device has to be supplied in this case with external energy, preferably electric energy, that has to be transported from the crane to the rope end. The energy lines and also the measuring devices are located directly on the load receiving member. This means, that the energy lines must be protected against external mechanical impacts, causing a significant technical effort that is accompanied with high costs.